Market adoption of wireless LAN (WLAN) technology has exploded, as users from a wide range of backgrounds and vertical industries have brought this technology into their homes, offices, and increasingly into the public air space. This inflection point has highlighted not only the limitations of earlier-generation systems, but the changing role WLAN technology now plays in people's work and lifestyles, across the globe. Indeed, WLANs are rapidly changing from convenience networks to business-critical networks. Increasingly users are depending on WLANs to improve the timeliness and productivity of their communications and applications, and in doing so, require greater visibility, security, management, and performance from their network.
As enterprises and other entities increasingly rely on wireless networks, monitoring and management of the components implementing the wireless network environments become critical to performance and security. Heretofore, it has not been recognized how important visibility into all layers of the network protocol is to optimization of network manageability and user performance in wireless LANs (WLANs). Unlike centrally-managed cellular wireless systems, known WLAN solutions use distributed access points to act as bridges between the wired infrastructure and the wireless clients, removing all physical and wireless media access protocol information from the protocol frames that are passed onto the infrastructure network. This results in uncoordinated handoffs of wireless clients moving between access points. An uncoordinated system of access points makes it difficult to manage a large number of access points, because there is no point of coordination. For example, known prior art wireless network systems such as conventional 802.11 systems provide the initial handshaking, access authentication and access association at a remote node without attention to overall network loading and signal quality.
This type of distributed architecture creates many problems affecting network management, mobility, and performance. Since each wireless LAN access point is a separate managed device, distributed architecture in general introduces many new managed elements in the network without sufficient attention to their global effects. Since the access points act in their own self-interest and are not aware of the actions taken by surrounding access points, they handle mobility (e.g., handoff actions) as a local event, which significantly increases latency.
U.S. application Ser. Nos. 10/155,938 and 10/407,357, identified above, disclose a hierarchical wireless network architecture that optimizes network management and performance of a relatively autonomously-managed WLAN. According to the system architecture, a central control element manages and controls one more access elements. These light-weight access elements perform real-time communication functions, such as data transfer and acknowledgements, while the central control element manages the connection between the access element and one or more wireless client devices.
Configuration of wireless network systems incorporating many managed access points can be complicated and time consuming. For example, configuration of the access elements in the hierarchical wireless network architecture disclosed above can be complicated and/or time consuming, especially where large numbers of access elements are deployed. Accordingly, it is desirable for access elements to include automatic configuration functionality that allows a network administrator to simply install an access element on a LAN and power it up. The access element may then automatically discover a central control element and receive configuration information. For example, U.S. application Ser. No. 10/394,905 discloses a light-weight access point protocol directed to the initialization, configuration and failover support tasks associated with access elements in a wireless network system.
FIG. 1 illustrates a hierarchical wireless network system where central control elements 24, 26 and access elements 12-15 communicate over respective LAN segments. As discussed in the above-identified U.S. patent applications, the communications interface between the central control element and an access element is typically a Layer 2 interface. Accordingly, when a new access element 12, for example, is deployed on a given LAN segment 10, it can be configured to automatically discover a central control element 24 by broadcasting discovery requests in an attempt to locate a central control element that responds to the discovery request. With knowledge of a responding central control element 24, for example, access element 12 can receive certain configuration information, such as a channel assignment, etc., and begin operation.
FIG. 2 illustrates a network environment where the central control element 24 is located on a different Layer 2 or Link Layer network than access elements 12-14, as well as access elements 12a-14a located on another LAN. As FIG. 2 illustrates, a router 51 is disposed between the LAN segment to which access elements 12-14 are connected and the LAN segment to which central control element 24 is connected. Similarly, router 51 also separates the LAN segment to which access elements 12a-14a are connected from the LAN segment associated with central control element 24. This deployment presents certain challenges both as to the initial, automatic configuration of access elements and re-configurations required by the failure of central control element 24. For example, to provide for failover support, access elements are typically configured to discover other available central control elements upon the failure of the central control element that was controlling the access element. In such an environment, however, Layer 2 discovery methodologies, such as broadcasting discovery requests, cannot be employed to discover central control elements on other Layer 2 networks that are separated by routers.
Possible solutions to this configuration obstacle include configuring the access elements to multicast discovery requests; however, not all networks support multicast, rendering this option inapplicable on a large number of network infrastructures. A second option is to require a network administrator to statically configure the newly-installed access element with the IP address of the central control element 24. This option can be problematic in large network deployments and, furthermore, does not address the requisite failover support. A third option is to extend the Dynamic Host Control Protocol (DHCP) functionality of the network to support vendor-specific extensions. Under such an option, when an access element requests and acquires an IP address from a DHCP server, the responding DHCP server may include the IP or other network address of central control element 24 in an extension to a DHCPOFFER packet. This option, however, requires the network administrator to change the DHCP configuration of the managed network, which is potentially more complicated and time consuming than other options. In any event, network administrators are often reluctant to change the configuration of a network once it is working properly. Lastly, a fourth option is to implement a VLAN to create a virtual LAN that allows for broadcasts of Layer 2 discovery requests to traverse router 51. Routers are typically installed to contain broadcast messages in smaller segments of the overall network to increase network efficiency. Configuration of a VLAN, thus, begins to undermine the very purpose for which routers are sometimes installed. In addition, the configuration of a VLAN, if not already implemented, requires changes to the underlying network infrastructure, which network administrators are hesitant to allow.
Accordingly, a need in the art exists for methods, apparatuses and systems that facilitate the deployment and configuration of managed access elements in a hierarchical wireless network system. A need in the art exists for methods, apparatuses and systems that facilitate deployment and configuration of access elements in a hierarchical wireless network system in a manner that seamlessly integrates with existing network infrastructures. Embodiments of the present invention substantially fulfill this need.